PT  - JOURNAL ARTICLE
AU  - Nidheesh Thadathil
AU  - Evan H Nicklas
AU  - Sabira Mohammed
AU  - Tommy L Lewis, Jr
AU  - Arlan Richardson
AU  - Sathyaseelan S. Deepa
TI  - Necroptosis increases with age in the brain and contributes to age-related neuroinflammation
AID  - 10.1101/2021.07.23.453580
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.07.23.453580
4099  - http://biorxiv.org/content/early/2021/07/25/2021.07.23.453580.short
4100  - http://biorxiv.org/content/early/2021/07/25/2021.07.23.453580.full
AB  - Chronic inflammation of the central nervous system (CNS), termed neuroinflammation, is a hallmark of aging and a proposed mediator of cognitive decline associated with aging. Neuroinflammation is characterized by the persistent activation of microglia, the innate immune cells of the CNS, with damage-associated molecular patterns (DAMPs) being one of the well-known activators of microglia. Because necroptosis is a cell death pathway that induce inflammation through the release of DAMPs, we hypothesized that an age-associated increase in necroptosis contributes to increased neuroinflammation with age. The marker of necroptosis, phosphorylated form of MLKL (P-MLKL), and kinases in the necroptosis pathway (RIPK1, RIPK3, and MLKL) showed a region-specific increase in the brain with age, specifically in the cortex layer V and the CA3 region of the hippocampus of mice. Similarly, MLKL-oligomers, which causes membrane binding and permeabilization were significantly increased in the cortex and hippocampus of old mice relative to young mice. Nearly 70 to 80% of P-MLKL immunoreactivity was localized to neurons and less than 10% was localized to microglia, whereas no P-MLKL was detected in astrocytes. P-MLKL expression in neurons was detected in the soma, not in the processes. Blocking necroptosis using Mlkl-/- mice reduced markers (Iba-1 and GFAP) of neuroinflammation in the brains of old mice and short-term treatment with the necroptosis inhibitor, necrostatin-1s, reduced expression of proinflammatory cytokines, IL-6 and IL-1β, in the hippocampus of old mice. Thus, our data demonstrate for the first time that brain necroptosis increases with age and contributes to age-related neuroinflammation in mice.Competing Interest StatementThe authors have declared no competing interest.